I know this is late so ignore if you are past this, but I just built up a CRF450r and found www.motostrano.com to be the ticket. They are pretty complete on motard stuff and I live in Northern Calif. so I can drive there.
I ended up using a SME catch can which runs your carb breathers into a long hose which is emptied after each ride. I used an aluminum water bottle for my radiator with some hose and barbed fittings from the hardware store (zip tied to frame in front). As for the crankcase breather, I extended it with a barbed coupler and hose from the hardware store and ran it into the airbox. I will probably put an in-line filter on it (made for pit bikes) or just leave it. It should not spill oil if everthing is working okay.
As for hard parts I started with one of their conversion kits and improvised from there. I also included a slipper clutch because I have one on my track sport bike and I love the wheel spin you get with them. A bit expensive but great for control.
Hope that helps, sorry for the late reply, I just logged on for the first time in a long time.